The 23-year-old goalkeeper joined Sunderland last summer on loan and was the first choice goalkeeper in the first half of the season.
However, he contracted Covid at the start of 2022 and was forced to miss a couple of games.
He came back straight into the team a week later, but Hoffmann claimed that he was yet to fully recover and was having physical difficulties.
The German revealed that the rapid antigen test he had to undergo still had traces of Covid and says Sunderland forced him to play regardless of him testing positive.
Hoffmann told German daily Bild: “When I came back after seven days of quarantine and went straight back in goal despite the rapid test being slightly positive.
“I had to play with Corona.
“I wasn’t doing well physically but the club wanted me to be tougher.”
He flew to Munich in February for further investigations into his health and never played a game again for Sunderland as they clinched promotion to the Championship.
Sunderland have responded to the claims with a statement, denying that they asked Hoffmann to play while he was positive.
“Sunderland AFC categorically refutes the allegations published earlier today by German newspaper Bild Sport”, it said.
“The report includes a number of false and inaccurate claims relating to Ron-Thorben Hoffmann and the Club has contacted the player’s representatives to clarify the comments made.
“SAFC complied with all Government and EFL guidance and protocols fully throughout the Covid-19 pandemic and continues to ensure the health and well-being of all staff is protected at all times.
“The Club will be making no further comment at this moment in time.”
